Silicon carbide (SiC) bipolar junction transistors (BJTs) are power devices capable of high-temperature operation and having low on-state and switching losses thanks to the high thermal conductivity, high breakdown electric field and high saturated electron drift velocity of SiC.
Silicon carbide is a semiconductor material having a wide bandgap and presenting a high melting point and physical properties (such as hardness) making it a suitable material for operation in harsh environments. These properties, however, may complicate the manufacturing of devices in SiC, at least for some of the processing steps such as e.g. etching. SiC can also form a large number of polytypes making the growth of single crystal substrate and high quality epitaxial layers difficult.
Silicon carbide substrates having an off-axis orientation are used to grow thick epitaxial layers with smooth morphology. There may however be material defects such as basal plane dislocations that may originate from the substrate and grow into the epitaxial layers. In power devices, such as SiC BJTs, the presence of such dislocations may cause degradation of the device's electrical parameters during operation.
Thus, there is a need for providing improved SiC BJTs and improved methods of manufacturing such BJTs that would alleviate at least some of the above-mentioned drawbacks.